"Existing configuration directory not found or does not contain a core.extension.yml file" error should be split into two cases, and say where it tried to look

[joachim-n]

Describe the bug

I am getting this error message when doing drush si --existing-config:

In SiteInstallCommands.php line 182:

  Existing configuration directory not found or does not contain a core.extension.yml
   file.".

To Reproduce What did you do?

Expected behavior

The error message should say which of the two things happened -- does the directory not exist, or is it missing core.extension.yml?

Also, it should tell me where Drush has tried to look - this is crucial to fix the problem: is Drush looking in the wrong place, OR is the place I told it to look contain bad data?

Actual behavior What happened instead?

Workaround Is there another way to do the desired action?

System Configuration

Q	A
Drush version?	11.5.1
Drupal version?	9.5
PHP version	8.1
OS?	Mac

Additional information Add any other context about the problem here.

[joachim-n]

Actually, a non-existent directory is picked up in validateConfigDir() so the problem is simpler -- it's just the message that is wrong.